$ \left(\dfrac{1}{256}\right)^{-\frac{1}{2}}$
$= 256^{\frac{1}{2}}$ To simplify $256^{\frac{1}{2}}$ , figure out what goes in the blank: $\left(? \right)^{2}=256$ To simplify $256^{\frac{1}{2}}$ , figure out what goes in the blank: $\left({16}\right)^{2}=256$ so $ 256^{\frac{1}{2}}=16$